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## read in date/time info in format 'm/d/y'
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## read in date/time info in format 'm/d/y'
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dates <- c("02/27/92", "02/27/92", "01/14/92", "02/28/92", "02/01/92")
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dates <- c("02/27/92", "02/27/92", "01/14/92", "02/28/92", "02/01/92")
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as.Date(dates, "\%m/\%d/\%y")
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as.Date(dates, "\%m/\%d/\%y")
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## date given as number of days since 1900-01-01 (a date in 1989)
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## date given as number of days since 1900-01-01 (a date in 1989)
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as.Date(32768, origin="1900-01-01")
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as.Date(32768, origin = "1900-01-01")
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## Excel is said to use 1900-01-01 as day 1 (Windows default) or
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## Excel is said to use 1900-01-01 as day 1 (Windows default) or
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## 1904-01-01 as day 0 (Mac default), but this is complicated by Excel
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## 1904-01-01 as day 0 (Mac default), but this is complicated by Excel
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## treating 1900 as a leap year.
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## treating 1900 as a leap year.
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## So for dates (post-1901) from Windows Excel
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## So for dates (post-1901) from Windows Excel
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as.Date(35981, origin="1899-12-30") # 1998-07-05
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as.Date(35981, origin = "1899-12-30") # 1998-07-05
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## and Mac Excel
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## and Mac Excel
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as.Date(34519, origin="1904-01-01") # 1998-07-05
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as.Date(34519, origin = "1904-01-01") # 1998-07-05
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## (these values come from http://support.microsoft.com/kb/214330)
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## (these values come from http://support.microsoft.com/kb/214330)
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## Experiment shows that Matlab's origin is 719529 days before ours,
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## Experiment shows that Matlab's origin is 719529 days before ours,
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## so Matlab day 734373 can be imported as
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## so Matlab day 734373 can be imported as
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as.Date(734373, origin = "1970-01-01") - 719529
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as.Date(734373, origin = "1970-01-01") - 719529
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## Timezone effect
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## Timezone effect
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z <- ISOdate(2010, 04, 13, c(0,12)) # midnight and midday UTC
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z <- ISOdate(2010, 04, 13, c(0,12)) # midnight and midday UTC
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as.Date(z) # in UTC
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as.Date(z) # in UTC
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\donttest{## these timezone names are common
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\donttest{## these timezone names are common
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as.Date(z, tz ="NZ")
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as.Date(z, tz = "NZ")
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as.Date(z, tz ="HST") # Hawaii}
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as.Date(z, tz = "HST") # Hawaii}
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}
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}
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\keyword{utilities}
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\keyword{utilities}
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\keyword{chron}
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\keyword{chron}